1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus which is capable of giving soft focus effects to digital image data, an image processing method, and a storage medium.
2. Description of the Related Art
There are various types of photographic camera lenses including soft focus lenses. A soft focus lens enables an image to be formed as if light were exuding from a highlighted portion of the image. Many of the soft focus lenses intentionally causes spherical aberration to thereby generate a soft-looking image.
Further, there has been known a method in which soft focus effects are obtained not by providing a lens with a soft focus function, but by using a filter. In this case, by mounting the filter at a front end of a photographic lens to thereby restrict light that passes through the filter, it is possible to achieve the same effects as obtained when shooting is performed using a soft focus lens, i.e. the effects of making the outline of a picked-up image slightly blurred.
In recent years, to achieve the soft focus effects by image processing has been proposed as one of methods of expressing an image picked up by a digital camera as a photograph. For example, a method has been proposed in which a blurred image is generated from an original image, and the blurred image is synthesized with the original image at a predetermined transmittance (see Japanese Patent Laid-Open Publication No. 2007-065784). In this technique, when the transmittance is set to 0%, the original image is used, and when the transmittance is set to 100%, the blurred image is used. The blurred image can be generated by applying a 2D Gaussian filter to the original image. Further, in Japanese Patent Laid-Open Publication No. 2007-065784, a method has been proposed e.g. in which instead of setting a uniform transmittance for en entire image plane, a face area is detected and a lower transmittance is set for the detected face area and a high-luminance portion is detected and a higher transmittance is set for the detected high-luminance portion. By thus adaptively changing an area to be soft-focused, it is possible to enhance the soft focus effects.
On the other hand, there has been proposed a method in which when synthesizing an original image and a blurred image at a certain addition ratio, the addition ratio at the time of monitoring is set differently from that at the time of printing (see U.S. Pat. No. 6,560,374). According to the method disclosed in U.S. Pat. No. 6,560,374, it is possible to add substantially the same soft focus effects to a small-sized image for monitor display and a large-sized image for printing.
As described above, by synthesizing an original image and a blurred image, it is possible to obtain the soft focus effects. However, the method disclosed in Japanese Patent Laid-Open Publication No. 2007-065784 suffers from a problem that when the data size of an original image is changed e.g. by a resizing process, the soft focus effects look different between a large-sized image and a small-sized image.
Further, in the technique disclosed in U.S. Pat. No. 6,560,374, the frequency characteristic of an input image is not taken into consideration, and hence the soft focus effects vary between images of different object types, such as a portrait and a landscape shot.